In recent years, electronic devices have become highly functional and compact. Accordingly, printed wiring boards that are highly functional and integrated are desirable. A build-up multilayer printed wiring board is designed to achieve a higher wiring density and integration. This type of wiring board can be formed by forming conductive circuits on a substrate and alternately laminating insulation layers and conductive layers on the substrate. The insulation layers can be made of resin such as polyimide resin and formed by applying a solution containing the resin to a substrate and curing the coating to form the insulation layer. However, the strength and rigidity of the wiring board having insulation layers made of resin may be insufficient, and thus stresses exerted from outside (for example, heat, impact from vibration, impact from being dropped or the like) may cause bending or warping in the entire wiring board.